The cells of the innate immune system, such as dendritic cells (DCs), provide an immune response that does not depend upon specific antigen recognition. See, for example, Tosi, J. Allergy Clin. Immunol. 116:241-49 (2005). Dendritic cells lack the highly specific antigen receptors of T and B cells, and rely instead on a set of pattern recognition receptors (“PRRs”), which recognize and bind pathogen-associated molecular patterns and thereby transduce an immune response signal. Fabrick et al., J. Biol. Chem. 279:26605-11 (2004). Illustrative of the class of PRRs are the Toll-like receptors (“TLRs”), which recognize a range of molecular patterns and generate intracellular signals for activating a number of host responses. Toll-like receptors such as TLR-9 detect microbial DNA by recognizing the presence of unmethylated cytidine-guanosine (CG) dinucleotides within certain base contexts, or “CpG motifs.” The interaction between microbial DNA and TLR-9 receptor induces cell signaling pathways which include mitogen-activated protein kinases and NFKB. These signaling events, in turn, provoke leukocyte gene expression and cytokine secretion. CpG motifs are not prominent in vertebrate genomes due to a phenomenon known as “CpG suppression,” but are present at the expected frequency in prokaryotic DNA. This contrast has been attributed to evolution of the vertebrate immune system to recognize unmethylated CpG motifs and respond with a coordinated cytokine response.